Numerical simulation of droplet transfer behavior in variable polarity gas metal arc welding

Zhao, Yangyang,Chung, Hyun Elsevier 2017 INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER - Vol.111 No.-

<P><B>Abstract</B></P> <P>Gas metal arc welding (GMAW) using an alternating current waveform is usually termed as variable polarity GMAW (VP-GMAW), during which the electrode polarity switches between positive and negative periodically. The arc properties and the droplet transfer in VP-GMAW would be different from traditional direct current GMAW. In order to clarify the droplet transfer phenomena during a VP-GMAW process, a unified numerical model including the interaction between the arc plasma and the moving droplet is developed. The simulation results indicate that the arc plasma generated at electrode negative polarity shows a less constricted shape, a lower plasma temperature and velocity, compared to positive polarity. The resultant droplet is found to have a bigger size and a lower temperature than that of direct current gas metal arc welding with the same average welding current. Moreover, a quantitative analysis of the heat fluxes into the electrode is further conducted to explain the thermal mechanism for the differences in droplet properties between variable polarity and direct current gas metal arc welding. Finally, the simulated results are compared with the high-speed images, and the simulated and experiment results show good agreements.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A unified arc-droplet model for variable polarity gas metal arc welding process is presented. </LI> <LI> Arc plasma properties using different polarities are investigated and compared. </LI> <LI> Droplet transfer behavior in variable polarity gas metal arc welding process is studied. </LI> <LI> Heat transfer behavior between the arc and the droplet is analyzed quantitatively. </LI> </UL> </P>

Influence of power source dynamics on metal and heat transfer behaviors in pulsed gas metal arc welding

Zhao, Yangyang,Chung, Hyun Elsevier 2018 INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER - Vol.121 No.-

<P><B>Abstract</B></P> <P>A numerical model has been constructed based on the solution of the magnetohydrodynamic equations within the framework of phase field algorithm to simulate the metal transfer process and to investigate the effect of power source dynamics on metal transfer and heat transfer behaviors in pulsed gas metal arc welding. Three typical kinds of power source dynamics (i.e. exponential, ideal square and trapezoidal waveform) using identical nominal pulsing parameters are considered and compared. The ideal square waveform with infinitely steep-sided pulse would lead to a higher detaching speed and an earlier detachment than other waveforms. Decrease in the response rate of the power source shows a retarding effect on the dynamic characteristics of the metal transfer, leading to a delay of detachment and a lower detaching speed. Moreover, this retarding effect is more and more significant as the response rate decreased and may even alter the transfer mode from one-drop-per-pulse to an undesired irregular pattern. Besides, a quantitative analysis of the heat fluxes into the electrode is further conducted, and the result shows that power source dynamics only has a quite slight influence on the heat transfer behavior.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A numerical study of the influence of power source dynamics in GMAW-P is presented. </LI> <LI> Ideal square waveform leads to higher detaching speed than other waveforms. </LI> <LI> Decrease in response rate of power source retards the detaching moment and speed. </LI> <LI> Effect of power source dynamics on heat transfer behavior is quite slight. </LI> </UL> </P>

Differential Profile of Plasma Circular RNAs in Type 1 Diabetes Mellitus

Yangyang Li,Ying Zhou,Minghui Zhao,Jing Zou,Yuxiao Zhu,Xuewen Yuan,Qianqi Liu,Hanqing Cai,Cong-Qiu Chu,Yu Liu 대한당뇨병학회 2020 Diabetes and Metabolism Journal Vol.44 No.6

Background No currently available biomarkers or treatment regimens fully meet therapeutic needs of type 1 diabetes mellitus (T1DM). Circular RNA (circRNA) is a recently identified class of stable noncoding RNA that have been documented as potential biomarkers for various diseases. Our objective was to identify and analyze plasma circRNAs altered in T1DM. Methods We used microarray to screen differentially expressed plasma circRNAs in patients with new onset T1DM (n=3) and age-/gender-matched healthy controls (n=3). Then, we selected six candidates with highest fold-change and validated them by quantitative real-time polymerase chain reaction in independent human cohort samples (n=12). Bioinformatic tools were adopted to predict putative microRNAs (miRNAs) sponged by these validated circRNAs and their downstream messenger RNAs (mRNAs). Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were performed to gain further insights into T1DM pathogenesis. Results We identified 68 differentially expressed circRNAs, with 61 and seven being up- and downregulated respectively. Four of the six selected candidates were successfully validated. Curations of their predicted interacting miRNAs revealed critical roles in inflammation and pathogenesis of autoimmune disorders. Functional relations were visualized by a circRNA-miRNA-mRNA network. GO and KEGG analyses identified multiple inflammation-related processes that could be potentially associated with T1DM pathogenesis, including cytokine-cytokine receptor interaction, inflammatory mediator regulation of transient receptor potential channels and leukocyte activation involved in immune response. Conclusion Our study report, for the first time, a profile of differentially expressed plasma circRNAs in new onset T1DM. Further in silico annotations and bioinformatics analyses supported future application of circRNAs as novel biomarkers of T1DM.

A Novel Feature Detection Algorithm Based on Improved 2DPCA- SIFT

AiliWang,Yangyang Zhao,Jiaying Zhao,Yuji Iwahori,Xinyuan Wang 보안공학연구지원센터 2015 International Journal of u- and e- Service, Scienc Vol.8 No.6

Stable local feature and representation is a fundamental component of many image registration, 3D reconstruction and object recognition algorithms. SIFT is a good descriptor that encodes the salient aspects of the image gradient in the feature point’s neighborhood. This paper improved SIFT- based local image descriptor and proposed a SIFT feature matching algorithm based on improved 2DPCA which can eliminate both rows and columns of relevance. Experimental results show that improved 2DPCA-SIFT algorithm is relatively stable, accurate and fast.

Medical Image Fusion based on Pulse Coupled Neural Network Combining with Compressive Sensing

AiliWang,Jiaying Zhao,Shiyu Dai,Yuji Iwahori,Yangyang Zhao 보안공학연구지원센터 2015 International Journal of Signal Processing, Image Vol.8 No.5

Image fusion is an important branch of information fusion, widely used in various fields, especially in medical field. So increasing the quality and efficiency of medical image fusion has great significance. Combining the advantages of pulse coupled neural networks with Compressive Sensing; this paper puts forward a novel image fusion method in NSCT transform domain. First, NSCT transform is applied to the source images, and the coefficients in low frequency coefficient are fused by mean rules. For high frequency coefficient, CS is applied and PCNN. Finally, inverse NSCT is applied to get the reconstructed image. The experimental results show that the fusion algorithm proposed in this paper in the performance and integration efficiency has better fusion results.

Optimal Configuration and Economic Operation of Wind–Solar-Storage Complementary System for Agricultural Irrigation in Mountainous Areas

Li Bin,Zhao Jianing,Zhang Yangyang,Bai Xiaoqing 대한전기학회 2023 Journal of Electrical Engineering & Technology Vol.18 No.4

The disorderly use of electricity in agriculture is a serious source of the current electricity tension, and as distributed energy is expediently promoted, it is becoming increasingly notable that the source network and load are not well coordinated. Small pumped storage power station is established in this paper using irrigation facilities and mountain height differences. On the basis of satisfying the electricity demand for irrigation, the capacity of pumping units and generating sets is configured prudently with wind farms and photovoltaic power stations. In addition, fluctuation smoothing is factored into consideration, the spectrum analysis method is utilized to calibrate the installed capacity. We develop a wind-solar-pumped storage complementary day-ahead dispatching model with the objective of minimizing the grid connection cost by taking into account the uncertainty of wind power and photovoltaic output and combining the complementary characteristics. The proposed model and method were validated through simulation on four typical days for a microgrid system. The simulation results demonstrate that the system fully utilizes new energy sources and successfully addresses the issue of water and electricity consumption for agricultural irrigation in mountainous regions. This system also offers a valuable concept for achieving low carbon and environmental protection for agricultural electricity consumption.

High step-up three-level DC-DC converter with three-winding coupled-inductor

Ding, Xinping,Zhao, Delin,Liu, Yun,Li, Kai,Hao, Yangyang The Korean Institute of Power Electronics 2020 JOURNAL OF POWER ELECTRONICS Vol.20 No.1

Due to the wide adoption of photovoltaic power generation, non-isolated high step-up DC-DC converters are becoming more and more popular. Among these converters, the switched/coupled-inductor-based converter is more attractive due to the fact that it has fewer power devices and a high efficiency. This paper presents a three-level high step-up DC-DC topology with a three-winding coupled-inductor. When compared with a conventional switched/coupled-inductor-based converter, a higher efficiency can be achieved, owing to low voltage stresses devices, fewer semiconductors in the power loop, lower current stresses, and ZCS of the main switches. The operating principle of the proposed topology is analyzed in detail via equivalent circuits, where a theoretical analysis is carried out using state space modelling. Experimental results obtained on a 24-300 V, 360 W lab prototype have verified the excellent performance of the proposed DC-DC converter.

Porous WO₃ monolith-based photoanodes for high-efficient photoelectrochemical water splitting

Wang, Yina,Zhang, Fangfang,Zhao, Guoyan,Zhao, Yingao,Ren, Yangyang,Zhang, Huijun,Zhang, Linyu,Du, Jimin,Han, Yumin,Kang, Dae Joon Elsevier 2019 CERAMICS INTERNATIONAL Vol.45 No.6

<P><B>Abstract</B></P> <P>We report a successful fabrication of low-cost, high-efficient, structurally-rigid, porous WO<SUB>3</SUB> photoelectrochemical (PEC) catalysts using polystyrene as the template by a sol-gel method and a high-temperature annealing treatment. The scanning electron microscopy and Brunauer-Emmett-Teller surface analysis results indicate that such WO<SUB>3</SUB> monoliths possess a porous structure and a large specific surface area, which can supply lots of photogenerated charge transfer pathways as well as more surface PEC active sites. Compared with a commercially available WO<SUB>3</SUB>, our highly porous WO<SUB>3</SUB> PEC catalysts show an excellent PEC water splitting activity. Particularly, the porous WO<SUB>3</SUB> photoanodes calcinated in the presence of oxygen atmosphere at 450 °C for 7 h show the best PEC performance exhibiting the photocurrent density of 0.97 mA/cm<SUP>2</SUP> at 1.23 V versus reversible the hydrogen electrode and the incident photon-to-current conversion efficiency up to 48.9% at 420 nm in 0.5 M Na<SUB>2</SUB>SO<SUB>4</SUB> electrolyte under AM 1.5 G irradiation. Such excellent PEC performance is due to the high porosity of the WO<SUB>3</SUB>, promoting the fast transfer and the separation rate of photogenerated carriers during the PEC water splitting process.</P>

3D Reconstruction of Remote Sensing Image Using Region Growing Combining with CMVS-PMVS

Aili Wang,Na An,Yangyang Zhao,Yuji Iwahori,Rui Kang 보안공학연구지원센터 2016 International Journal of Multimedia and Ubiquitous Vol.11 No.8

The characteristics of remote sensing image is not obvious and can not reflect the be reconstructed the detail characters of the objects. For the sparse points in multi images fusion results, texture selection and it is relatively difficult problems, for accurate reconstruction of remote sensing image details, this paper presents CMVS-PMVS(cluster multi view stereo- patch based multi view stereo) combining with region growing for computing dense matching points. First, select some seed points by region growing algorithm, and find the matching relationship between the seed points, followed by the matching relation from the seed point to spread until to the entire image. Then the image set are clustered by CMVS in order to reduce the amount of data in the process of reconstruction, and the operation rate and reconstruction accuracy can be improved. PMVS reconstruction method is used to complete the reconstruction task by matching, expanding and filtering three steps. The experimental results showed that the point cloud is dense enough which are reconstructed by the 3d reconstruction algorithm based on regional growth combining CMVS-PMVS and well expressed the practical model of object reconstruction, the reconstruction of objects in remote sensing images has very strong practicability.

Robust Security Control Under Denial-of-service Jamming Attacks: An Event-triggered Sliding-mode Control Approach

Bo-Chao Zheng,Lina Guo,Yangyang Zhao,Xiaoguang Liu,Zhou Gu 제어·로봇·시스템학회 2022 International Journal of Control, Automation, and Vol.20 No.12

Robust security problem for uncertain cyber-physical systems (CPSs) subject to periodic denial-ofservice (DoS) jamming attacks is investigated based on event-triggered (ET) sliding-mode control (SMC) approach in this paper. First, a new type of SMC approach driven by ET mechanism is constructed using the property of the period DoS jamming attacks. Then, sufficient conditions for robust stabilization of dynamical systems constrained by system parameters and attacks period are proposed. Further, it is proved that the execution time interval of the proposed ET-based SMC strategy has a positive lower bound, and thus Zeno-free behavior occurs during system evolution. Finally, comparisons results show the effectiveness and superiority of this methodology.